I’m sure we’ve all seen poor specifications for windows and doors. Sometimes they have just minor errors that can be worked around but sometimes more serious ones that can lead to confusion and even disputes. But I think I may have come across the most out of date specification ever.

Firstly, a little background on the standards we have in our industry. Back in the late 80s when we drafting British Standards for PVC-U profiles and PVC-U windows, there was a dispute between the users of two different types of material. The bulk of the industry used so called impact modified materials but a significant part of the industry used unmodified material. The former contained an added ingredient designed to improve the impact resistance of the profile, the latter didn’t. Both appeared capable of making good windows but the unmodified material allegedly needed more careful handling during manufacture to avoid, inter alia, chipping when being sawn. I think I’m right in saying that the British Plastics Federation required members to used only impact modified material but I could be wrong (I know, I know; very unlikely). To separate the two materials, the impact modified lobby increased the drop height of the cold temperature impact test from 1m to 1.5m but the unmodified lobby wanted to keep the 1m drop height used throughout Europe. BSI decided the only way to accommodate the two was to produce two British Standards for PVC-U profiles – BS 7413 for impact modified materials or “material type A” and BS 7414 for unmodified materials or “material type B”. BS 7413 sold in big numbers and I think BS 7414 sold one copy! This was in 1991 and when the first revision time came around, the companies that used the unmodified material for whatever reason had changed to using modified material and BS 7414 was withdrawn. So in the mid 90s the terms “material type A” and “material type B” were dropped and we were left with just BS 7413. At the same time we were busy in CEN drafting a European Standard for PVC-U profiles for windows and doors and EN 12608 was published in the early part of this century and BS 7413 was withdrawn. So “material type …” has not been used for knocking on 15 years and BS 7413 has not been around for best part of a decade. So you would think these would not be seen again. Ha! As if. I have come across a specification that includes the requirement for suppliers to use profiles in accordance with BS 7413 using material type A.

Now, I know specifiers have to be so familiar with lots of different products but to use a 15 year old standard smacks of carelessness or worse. It looks like an old specification has been taken off the shelf and dusted off with no checking as to whether the requirements were up to date.

I still get telephone calls concerning old BPF publications such as codes of practice for survey and installation that were revised years ago. In fact, trade codes of practice for survey and installation were superseded by a revised BS 8213-4 in 2007 after collaboration between the 4 main material federations to produce a code of practice for the survey and installation of windows and doorsets of any material. I suppose it’s fair enough that perhaps knowledge of this updated code has not percolated down to all specifiers yet, but there is absolutely no excuse for using a 15 year old standard. A quick check on BSI’s web site would provide the necessary knowledge that all the versions of BS 7413 have been withdrawn or superseded.

However, while this may be one of the more glaring errors in specifications, it is by no means the only one. It was for that reason the BPF published a brilliant document (modesty forbids mentioning who wrote it) PVC-U windows and doorsets – Standards, Sustainability, Specification (available from www.bpfwindowsgroup.com for £40 hard copy or £20 in pdf format). For the purposes of this article, it is the specification bit I am referring to, but the other sections are considered useful too for informing the uninitiated of the various aspects of PVC-U windows and doorsets.

Many specifiers are unaware of how to specify PVC-U windows not knowing, for instance, the difference between welded and mechanically jointed mullions and transoms or the different weld finishing techniques – knifing, grooving, polishing – or what their responsibilities are in providing information to the manufacturer. The document explains what a specification should include and how to include it. This 62 page document will guide a specifier through the labyrinth of information (and  dis‑information) surrounding PVC-U windows and the last few pages contain a sample specification with a explanatory commentary on each element. There is no reason why a good specification for PVC-U windows should extend beyond a couple of pages for the basic elements. That’s why all the effort has been expended over the years in drafting British and European Standards – so that specifiers don’t have to make up their own requirements confusing the window suppliers and inevitably leading to conflicts. I remember my early days in this industry nearly 30 years ago selling to local authorities and health authorities when the specifications ranged from a pathetic  “windows shall be white PVC” to documents running to 15 pages or more detailing such esoteric things as the position and thickness of internal webs in the profiles. I earned my corn selling not windows but the specification for those windows. Regrettably, many authorities bought naively in those days making their decisions purely on price, and that is why many ended up with externally beaded windows with the cheapest of the cheap *censored*spur handles, single glazed and generally pretty useless all round. Many of these windows are now being replaced with modern ones that are thermally efficient and much, much more secure. I had thought that these new windows would be being properly specified but it looks like my optimism was misplaced in some cases. BS 7412 contains just about all a specifier needs to procure high quality PVC-U products leaving just window styles and other such preferences to be decided on.

So, if you are experiencing poor specifications, it may be worth shelling out a few quid and using this comprehensive document to educate your specifiers .

Paul Jervis

25th February 2009